Gas chromatograph

ABSTRACT

A compact, efficient, portable gas chromatograph system is disclosed in which the gas chromatographic column is disposed in a closed loop with an electrolytic hydrogen generator-separator. The output from the column containing the bands of analyzable materials dispersed in hydrogen carrier gas is passed through the tubular anode of the generator-separator. The hydrogen passes through the wall of the anode, across the electrolyte through the wall of the cathode and is collected and returned by way of the sample inlet to the inlet to the column. The analyzable material remaining stalled within the anode tube is swept into the detector by an auxiliary electrolytic hydrogen generator. A pressure transducer downstream from the anode develops an increased voltage signal in response to pressure drop which is applied to the controller for the auxiliary hydrogen generator to maintain a constant flow of hydrogen carrier gas within the closed loop circuit while also maintaining a flow of hydrogen sweep gas to the detector.

VOLTAGE Jan. 7, 1975 GAS CHROMATOGRAIPH [57] ABSTRACT [75] Inventor:Mario R. Stevens, Glendora, Calif. A compact, ffi i t portable gaschromatograph [73] Assignee: California Institute of Technology, temdlsfllosed in Whlch the gas Chromatographic v Pasadena C lif umn isdisposed in a closed loop with an electrolytic hydrogengeneratonseparator. The output from the [22] Filed: Mar. 5, 197.3 columncontaining the bands of analyzable materials 211 App] 33 237 dispersedin hydrogen carrier gas is passed through the tubular anode of thegenerator-separator. The hydrogen passes through the wall of the anode,across the [52] 23/232 C, 23/254 electrolyte through the wall of thecathode and is col 55/158 lected and returned by way of the sample inletto the [51] lllit. Cl. Gllln 31/08 inlet to the Column The analyzablematerial rel-aim [58] Flew of Search 73/231 27 R; 55/16 ing stalledwithin the anode tube :is swept into the de- 55/197; 23/232 254 R1 254255 tector by an auxiliary electrolytic hydrogen generator. 255 E? 48/61A pressure transducer downstream from the anode develops an increasedvoltage signal in response to pres- [56] References Cited sure dropwhich is applied to the controller for the UNITED STATES PA EN Sauxiliary hydrogen generator to maintain a constant 3,400,650 9/1968Burg 23/281 x flow of y g Carrier g within the closed 1001) 3,468,7819/1969 Lucero 1 55/16 X circuit while also maintaining a flow ofhydrogen 3,589,171 6/1971 Haley v 73/231 sweep gas to the detector.3,690,835 9/1972 Lovelock 1 1 1 73/231 X r 3,701,632 10/1972 Lovelock 4.73/27 R X Primary ExaminerRichard C. Queisser 15 Claims 6 Drawingfigures Assistant Examiner-Stephen A. Kreitman Attorney, Agent, orFirmMarvin E. Jacobs CONTROLLER Patented Jan. 7, 1975 3 Sheets-Sheet 1VOLTAGE CONTROLLER POWER SUPPLY T0 AUXILIARY GEN FIG. 4

atnted Jan. 7, 1975 3 Sheets-Sheet 2 FIG.

FIG.

atented Jan. 7, 1975 3,858,435

5 Sheets-Sheet 5 N :K V

HEAT INJECT ON SAMPLE 4 /CO\ TIME, min

FIG. 5

AIR

ORIGIN OF THE INVENTION The invention described herein was made in theperformance of work under a NASA contract and is subject to theprovisions of Section 305 of the National Aeronautics and Space Act of1958, Public Law 83-568 (72 Stat. 435; 42 USC 2457).

, BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a gas chromatographic system, methods of analysisand more particu larly to a compact, efficient and reliable hydrogencarrier gas gas-chromatographic system.

2. History of the Prior Art Analysis of complex samples of matter isgreatly facilitated by gasifying the sample and then passing it ingasified form through a device suchas a gas chromato- 0 graph whichseparates the components of the sample into sequential bands ofanalyzable components. In a gas chromatograph or other separationapparatus, gas or vapor sample to be analyzed is transported through thevarious functional parts of the apparatus by a stream of inert carriergas. While this procedure facilitates automation of analysis, it doeshowever introduce other problems.

Thus, sample constituents present in minute quantities are so greatlydiluted by the much larger quantity of carrier gas necessary foroperation of the chromato graph column that they may be difficult orimpossible to detect. Furthermore, the pressure and flow rate of theeffluent emerging from the chromatograph may exceed the capability of adetector such as a mass spectrometer or an ionization cross-sectiondetector. Moreover, many detectors, such as gas density balance, thermalconductivity or ionization cross-section, are concentration dependentand variation in flow rate or excessive dilution of the sample in thecarrier gas affects both precision and accuracy of analysis.

Various approaches to interfacing a gas chromatograph to a detector havebeen suggested, such as scaling down the dimensions of the chromatographto suit the needs of the detector, interfacing the chromatograph and thedetector with a capillary column or by the use of various plasticmembranes or a fritted glass surface to separate carrier gas beforeintroduction of the effluent into the detector. None of these approacheshave been entirely satisfactory.

A much improved technique utilizing a heated palladium film as aselective hydrogen transfer device is disclosed in U.S. Pat. Nos.3,638,396, 3,638,397 and 3,589,] 7 l. Optionally a steady flow of asecond carrier gas impermeable to the palladium film such as helium canbe introduced into the transfer device to sweep the sample into thedetector. However, these systems require the use of auxiliary gascylinders and associated valving to supply and meter the flow of carriergas.

A substantial simplification was provided by the electrolytic hydrogengenerator-separator disclosed in US. Pat. Nos. 3,690,835 and 3,701,632in which the hydrogen carrier gas generation function was combined withthe gas separation function in a single device. However, it was founddifficult to operate the generatorseparator with a residual uniform flowto sweep the sample into the detector. Furthermore, loss of hydrogenfrom the system upset stoichiometry of the electrolytic cell and aftersustained periods of operation, metal loss occurred leading toperforation of the electrodes of the generator-separator cell.

SUMMARY OF THE INVENTION The gas chromatographic system of the inventionis completely self-contained and portable and is selfsustaining exceptfor the requirement of small additions of water (5l5 cc/day). The systemis highly versatile and exhibits high reliability and accuracy. Thepresent lower limit of detection is of the order of 1-10 ppm ofmaterials such as ethane. The system does not require an external heavysource of pressurized carrier gas.

Unlike previously reported gas chromatographs, the present system iscapable of universal analytical appli cation and at the same time iscompletely independent of any external source of carrier gas supply orpower. The portable gas chromatograph of the invention will find use inthe on-site surveillance and monitoring of atmospheric pollution,confined atmospheres in mine shafts, plants or buildings and stationarysources, such as industrial smoke and stack emissions.

The chromatographic system of the invention generally comprises acontinuous hydrogen carrier gas circuit including a gas chromatographiccolumn and an electrolytic hydrogen gas generator-separator device. Theoutput from an auxiliary hydrogen generator is introduced into thecircuit upstream. from the generatorseparator device and a sample inletis disposed upstream from the column. A detector disposed down streamfrom the device senses the components of the dispersed sample and ventsthe dispersed sample. A pressure sensing means senses the pressuredownstream from the generator-separator device and develops a signalwhich is utilized to control the output of the auxiliary hydrogengenerator.

These and many other features and attendant advantages of the inventionwill become readily apparent and the invention becomes better understoodby reference to the following detailed description when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagrammatic view ofthe gas chromatographic analysis system of the invention;

FIG. 2 is a cross-sectional view of the generatorseparator;

FIG. 3 is a cross-sectional view of the auxiliary hydrogen generator;

FIG. 4 is a schematic of the controller for the auxiliary hydrogengenerator;

FIG. 5 is a chromatogram of a simulated Martian atmosphere; and

FIG. 6 is a chromatogram of an air mixture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The system as shown in FIG. 1generally comprises a gas chromatographic .column 12, an electrolyticgenerator-separator device 14, an auxiliary electrolytic hydrogengenerator 16 and a detector 18, such as an ionization cross-sectiondetector. The column 12 and the generator-separator 14 form part of acontinuous, closed circuit 10. The circuit 10 also includes a pressuregauge 20 and an inlet assembly 241. The inlet assembly, disposed justupstream of the inlet 26 to the column 12, includes an injection port 28and a collection port 30 secured to different segments 32, 34 of theassembly. The ports 28, 30 can be isolated from each other and from thecircuit by means of three-way walves 36, 38.

The generator-separator 14 includes an anode 40 having an open inlet end42 and an open outlet end 44. The cathode 46 has a closed end 48disposed within the body 50 of the electrolyte and an open outlet end52. The electrolyte 50 is contained in a housing 45 which may beexternally heated by a coil 47 powered by a variable power source, notshown. The output from the column outlet 54 combines with the outputfrom the outlet 56 from the auxiliary generator 16 atjunction 58 and isswept into the inlet 42 to the anode. The outlet 56 is isolated from theinlet by means of check valves 57, 59.

A major portion of the hydrogen carrier gas transfers through the wallof the anode 40 across the electrolyte 50 and through the wall of thecathode 46, collects therein, and returns through the circuit 10, sampleassembly 24 to the inlet 26 to the column 12. The sample dispersed inthe remaining hydrogen leaves the generator-separator device 14 throughthe anode outlet 44 and passes through the flow restrictor 60' into thedetector 18.

A pressure transducer 62 placed across restrictor 60 senses the changeof pressure in the anode 40 and develops a control signal which isapplied to the voltage controller 64 for the auxiliary hydrogengenerator 16. The voltage controller 64 controls the auxiliary generator16 to provide a steady flow of sweep gas through the anode 40 andcompensate for any variation in the hydrogen transfer through the anode40, i.e., the variation in generator-separator performance due to thepresence of eluted gas components in the anode.

The auxiliary hydrogen generator is employed in the chromatographiccircuit for the following reasons. The hydrogen generator-separator isthe carrier gas source and absorber (sink) for the chromatographiccircuit, as indicated by the arrows. As the carrier gas (carrying asample of gas from the column) flows from the column into the hydrogengenerator-separator, greater than 99.96 percent of the hydrogen isremoved from the circuit at the anode.

Residual hydrogen pressures of approximately 10 to torr have beenexperimentally noted at the ancan be transferred through the anode wallunder the balanced operating conditions of the hydrogengenerator-separator. It does not, therefore, permeate through the anodewall, but instead mixes with non-hydrogen components as they proceed tothe detector.

When the main carrier stream, containing nonhydrogen components, entersthe anode, the amount of hydrogen transferred at the anode walldecreases. This decrease will cause variations to occur in the hydrogencarrier gas flow rate if it is not compensated for. The anode willattempt to maintain the constant transfer rate by utilizing hydrogennormally associated with the auxiliary carrier gas stream. In so doing,the pressure in the line, downstream of the anode, will fall. Thispressure decrease is sensed by the pressure transducer whose increasedoutput signal will immediately cause more voltage to be applied to theauxiliary hydrogen generator. The additional hydrogen generated entersthe system and will in effect maintain the constant flow of hydrogenwithin the closed-loop circuit, while also maintaining a flow ofhydrogen to the detector.

The need for a separate detector may be obviated should advantage betaken of the variation in the anode behavior when a non-hydrogencomponent is in the gas stream within it. This behavior is manifested interms of a current variation as disclosed in Pat. No. 3,701,632.Amplification of this signal will let the anode serve as an excellentchromatographic detector. The intensity of the signal will beproportional to the concentration of the non-hydrogen components as wellas its chemical affinity for palladium. Calibration must be donecarefully.

While ambient air will be separated from samples by the chromatographiccolumn, all the oxygen is quantitatively converted to water in theanode, requiring good temperature control at the detector to preventcondensation of this water. Also, certain unsaturates eluting from thecolumn will undergo hydrogenation at the anode leading to a multiplicityof signals at the detector. Thus, in the calibration for unsaturatedcompounds this problem should be realized.

The portable, self-contained gas .chromatograph has been successfullyoperated continuously for a period of ode. Under normal chromatographicoperations,,only

the sample gases would remain in the anode. These gases would stagnatethere, except for diffusion and residual directional momentum, and wouldnot be able to reach the detector. This is avoided by using a smallquantity of an auxiliary carrier gas, in this case also hydrogen, toflush these non-hydrogen components out of the anode to the detector.

When the GC is being prepared for use, the carrier gas flow is firstadjusted for no-sample conditions. Electric energy is applied to thehydrogen generatorseparator so that there is a gas flow circulatingwithin the closed-loop circuit. The output of the pressure transducerwhich senses the pressure drop through the flow restrictor, is adjustedto provide sufficient voltage to the auxiliary hydrogen generator toproduce from 0.1 cc to 1 cc hydrogen flow per minute, as required by aparticular analysis. This additional hydrogen is led into theclosed-loop circuit through a check valve at that junction. Thishydrogen is in excess of that which 4 months. Maintenance was minimaLtheaddition of small amounts of water (5-15 cc/day) to the auxiliaryhydrogen generator daily accounting for virtually all of themaintenance. The system is completely portable, using a power packconsisting of two l2-volt batteries and one 6-volt battery. The devicehas a volume of less than 1 cubic foot and weighs less than 40 pounds,including a 20-pound power pack. It is independent of all externalsources of supply.

FIG. 2 illustrates a suitable form of the electrolyticgenerator-separator. The carrier gas is hydrogen of high purity and theelectrodes are formed of a material impermeable to all gases below acertain temperature and selectively permeable to hydrogen when. heatedto a temperature above about C. Palladium and its alloys are remarkablypermeable to hydrogen as long as heated to a temperature above about100C to C.

Pure palladium when subject to temperature cycling in the presence ofhydrogen, suffers mechanical distortions. However, an alloy of palladiumcontaining 10 to 30 percent silver, preferably about 25 percent silver,is as permeable to hydrogen and is mechanically stable. Other palladiumalloys, for example, palladiumrhodium alloys may confer more resistanceto corro sion to the films and extend the useful life of thegenerator-separator. The palladium tube maybe provided in variousconfigurations and lengths of tubing may be connected in parallel toprovide increased surface area with less flow resistance. Membranes ortubes can also be formed from a base structural material such as aporous ceramic coated with a thin, continuous film of palladium or asuitable hydrogen permeable palladium alloy. The hydrogen flux for agiven hydrogen pressure difference through a thin film of palladium oralloy is dependent on tube geometry, wall thickness and walltemperature.

To maintain the palladium film at a temperature at which it is permeableto hydrogen the cell may be heated by various means such as by disposingit in an oven or by heating the device electrically. For example, theheating coil 47 may be utilized to raise the electrodes 40 and 46 andthe electrolyte 50 to a temperature above 200C. Though it is desirableto maintain the resistance of the electrodes and electrolyte as low aspossible for the purposes of electrical power efficiency, theelectrolytic cell may in some configurations provide a sufficientinternal impedance to produce the desired heating on passage of currentthrough the electrodes and electrolyte. In other configurations, theheat supplied by operation of the electrolytic cell contributes to theheat received to maintain the films at the desired temperature. Thus,the electrolysis'current supplied by the electrolysis power andcontroller unit, not shown, may also be utilized to provide a portion ofthe necessary heating.

The electrolyte is a material capableof transporting an ionic species ofthe carrier gas from one electrode to the other, is inert with respectto the electrodes, is

stable at the temperature of operation and is capable of regeneratingthe carrier gas by electrolytic association or disassociation as isrequired. The electrolyte may be an acid, basic or salt material and ispreferably an inorganic metal hydroxide.

The most suitable materials for use in the invention are the Group 1metal hydroxides such'as sodium hydroxide, potassium hydroxide, orlithium hydroxide. The hydroxides should be utilized in a hydrated form,preferably contain 10 to 35 percent water of hydration since this bothlowers the power requirement and the temperature at which theelectrolyte becomes molten. Improved operation of the cell occurs whenat least 10 to 25 percent of the lighter weight lithium hydroxide ismixed with sodium or potassium hydroxide, preferably the latter.Commercial potassium hydroxide containing 25 percent water melts at275C. The addition of 10 percent lithium hydroxide to this electrolytefurther lowers the temperature at which the electrolyte becomes moltento about 200C.

The fused electrolyte utilized must be very pure to provide continuous,trouble-free operation. The initial supply of hydrogen carrier gasshould also be pure to avoid analytical error. It is important tomaintain the temperature of the anode tube above the critical diffusiontemperature so that a sufficient supply of hydrogen is maintained in theelectrolyte at all times. It is also desirable that the tube beactivated prior to assembling the cell and is preferable thatmetalsother than palladium silver or gold not be present in the cell.

Referring now in detail to FIG. 2, the illustrated generator-separator14 includes a flanged housing 70 enclosed by a cap 72, secured by bolts.not shown. The

interior cell recess 74 is surfaced with an insulator liner 76, suitablyformed of Teflon (polytetrafluoroethylene). The cap 72 is fitted withthree feedthrough ports which electrically isolate the anode inlet 42,anode outlet 44 and cathode outlet 52 while providing a positive sealfor the cell contents. An annular disc 80, suitably formed of Pd/Ag,contains ports which sealingly receive and support the anode inlet 42and anode outlet 44. A cap liner 78 insulates the cap 72 from the disc80, and a cathode liner sleeve 81 insulates the disc from the cathode46.

In an illustrated embodiment, both electrode assemblies are fabricatedfrom palladium/silver alloy tubing. The center electrode 46 is thecathode. It is a tightly wound spiral, 0.67 meters in length, closed atthe bot tom end. The spiral consists of 12 loops, each loop pro- 7viding 1 cm of cathode surface area. The anode assembly is positioned soas to surround the cathode in the form of a loosely wound spiralapproximately 2 meters in length. The anode 40 is open at both ends. Gasenters the anode from the chromatographic column and leaves the otheranode on its way to the detector.

Both electrodes are immersed in an electrolyte. The cell is operated at200C to 250C. Higher temperatures are avoided to prevent failure of thecell liner. Under such operating conditions, the pressure within thecell body is only slightly above atmospheric and arises mainly from theexpansion of the trapped air plus the vapor pressure of water.

There is no complete understanding or description of the process bywhich a palladium alloy electrode permits the transfer of hydrogenthrough its wall. In practice the hydrogen transfer is governed by thetempera ture of the electrolyte, the applied potential, the electrodethickness, and the hydrogen concentration gradi-- ent. Nevertheless, thecell reaction may be considered as follows:

The forward reaction occurs at the cathode, where hydrogen istransported from the electrolytic side of the hollow electrode to theinside wall of the electrode. The reverse reaction takes place at theanode where gaseous hydrogen is transferred through the electrode wallinto the electrolyte. Hydrogen flows from the cathode through the GCcolumn and is removed from the gas stream at the anode. It is noted thatthe electrolytic reaction does not include the formation of oxygen. Thisis the main reason why' the cell body pressure is only slightly aboveambient when the cell is operating. While the flow of hydrogen followsdirectly from Fara= days Laws of Electrolysis, the actual operationefficiency of the cell is cathode limited.

Maximum efficiency is attained when the cathode current density is0.1,amp/cm of cathode surface area. For the system shown, then, theoptimum hydrogen flow is 8.4 ml/min at a maximum operating current of1.2 amps. Generation of this quantity of hydrogen is accomplished at 0.2V or less. Thus, the maximum power of 0.24 watts required is far lessthan that associated with the direct electrolysis of water (1.86 watts)for an equal amount of hydrogen.

FIG. 3 illustrates the construction of a second electrolytic cell,designated the auxiliary hydrogen generator 16. The cell body 90,suitably formed of nickel, which serves as the anode, is a hollowcylinder. It is threaded at the top to accept a cell cap 92 fitted witha hydrogen outlet line 94 and an oxygen vent 96. Internally, thehydrogen outlet is connected to the cathode assembly 98 which consistsof a palladium/silver tube 100 in the form of a tightly wound helix heldin place at the bottom of the cell body by means of a Teflon spacer 102.The top part of the cathode tube is attached by a gold-platinum tube 104to the hydrogen outlet line 94. The line 94 is insulated by means of anepoxy seal 106 at the cell cap. The cathode assembly is immersed withinan electrolyte 108, suitably a 10 percent KOH aqueous solution.

The controller for the auxiliary hydrogen generator is illustrated inFIG. 4. The controller 200 includes a first amplifier 202 receiving thesignal from the transducer 62. A second amplifier having a variableresistor 204 input for the pressure set further amplifies the signal andapplies the signal to the power supply 206 for the auxiliary hydrogengenerator. With no sample in the gas chromatograph and with the mainhydrogen carrier gas flow circulating within the closed loop circuit,the output of the pressure transducer which senses the pressuredownstream of the anode, but upstream of the flow restrictor is adjustedby means of variable resistor input 204 to provide sufficient voltage tothe auxiliary generator to produce from 0.1 to 1.0 cc hydrogen flow perminute as required by the particular analysis.

When non-hydrogen components enter the anode, the decrease in hydrogentransfer causes variations to occur in the hydrogen carrier gas flowrate if it is not compensated for. The anode will attempt to maintainthe constant transfer rate by utilizing hydrogen normally associatedwith the auxiliary carrier gas stream. In so doing, the pressure in theline, downstream of the anode, will fall. This pressure decrease issensed by the pressure transducer whose increased output signal willimmediately cause more voltage to be applied to the auxiliary hydrogengenerator. Additional hydrogen which is generated enters the system andwill in effect maintain the constant flow of hydrogen within theclosed-loop circuit while also maintaining a flow of hydrogen to thedetector. The power requirements for the unit will vary, but will notexceed 10 W. Maximum operation efficiency is achieved when the system isoperated at 80C. The heater will require an additional 10 W.

The chromatographic system utilizes chromatographic column ofconventional design and characteristics. In the illustrated embodiment,the chromatographic assembly included 0.16 cm i.d. tubular columns(packed or open type) of variable length excluding heating elements,thermocouples, and electrical connections. Each assembly is anindependent unit. A

typical unit measures 15 cm X 2.54 cm o.d. Maximum power required toheat the unit is 30 W, with 10 W normally used.

EXAMPLE I A simulated Martian atmosphere comprising a mixture of theminor component (0.1) gases shown in FIG. 5 dispersed in a matrix of COwas analyzed.

The column was 1.2 meters long, 0.16 cm i.d. stainless steel packed withmolecular sieve 5A. The column was temperature programmed, ambient to200C, with the first four peaks eluting under ambient temperatureconditions. A heating rate of 33C/min was then applied, with a maximumtemperature of 220C being achieved within 7 minutes. The total run wascompleted in 12 minutes.

EXAMPLE 2 An analysis of a three-component gas in air was conducted inthe system of the invention utilizing a 1 meter long stainlesssteelcolumn having a 0.16 cm i.d. packed with Parapak R & Q in series, each0.5 meter long. The hydrogen flow through the closed-loop was 3.5 cc/minand through the detector was 2.8 cc/min. The column was maintained atambient-temperature.

FIG. 6 is a chromatogram of the'three-component gas mixture in air. Thethree minor components made up 33 percent of the sample volume. In thiscase the auxiliary carrier gas flow was almost equal to that of the maincarrier gas flow. The minor component chromatographic peak intensity maybe enchanced by sim ply reducing the auxiliary carrier gas flow relativeto the main carrier gas flowrate.

The portable self-contained gas chromatograph has been developed andsuccessfully operated continuously for a period of four months.Maintenance was minimal, the addition of small amounts of water (5-15cc/day) to the auxiliary hydrogen generator daily accounting forvirtually all of the maintenance.

The system is completely portable, using a power pack consisting of two12-volt batteries and one 6-volt battery comprising a total of 9.07 kg.It is independent of all external sources of supply. It should be ofvalue in air pollution studies, study of confined atmospheres, as inmine shafts, on stream studies of industrial smoke and stack exhaust.Utilizing the simulated Martian atmosphere, it was determined that thesensitivity limits of the system are in the range of l-l0 ppm for C 11It is to be understood that only preferred embodiments of the inventionhave been described and that numerous'substitutions, modifications andalterations are all permissible without departing from the spirit andscope of the invention as defined in the following claims.

What is claimed is:

l. An analysis system comprising:

- a closed hydrogen circuit including a gas chromatographic column andan electrolytic hydrogen carrier gas generator-separator including aselectively hydrogen permeable anode electrode and cathode electrode,the inlet to the column being connected to the hydrogen carrier gasoutput from said cathode and the outlet from said column being connectedto a first inlet end of said anode;

sample inlet means connected to said circuit upstream of said columninlet;

an auxiliary electrolytic hydrogen generator having a sweep gas hydrogenoutput connected to the first end of said anode;

detector means connected to the second end of said anode for receivingand analyzing a dispersion of samples in said sweep gas;

pressure detector means for sensing the pressure of the second outletend of said anode and developing an electrical signal indicativethereof; and

electrical controller means receiving said signal for controlling theoutput of said auxiliary generator.

2. An analysis system according to claim 1 in which said controllermeans includes a first output element for providing a substantiallyconstant control signal for providing a minimum constant flow rate ofhydrogen sweep gas in excess of the amount of gas permeating through theanode of the generator-separator.

3. An analysis system according to claim 2 in which said pressuredetector means includes a transducer for developing an electrical signalinversely proportional to said pressure change and said controllerincludes a second control element for developing a control signal forchanging the flow rate of said auxiliary generator above said minimumrate in response to changes in the hydrogen flow rate change throughsaid anode.

4. An analysis system according to claim 1 in which said detector meansis an ionization cross-section detector.

5. An analysis system according to claim l in which said auxiliarygenerator is an electrolytic cell for the electrolytic decomposition ofwater into hydrogen and oxygen.

6. A system according to claim 5 in which said auxiliary hydrogengenerator includes a palladium-silver electrode selectively permeable tohydrogen.

7; An analysis system according to claim 1 in which the electrodes ofsaid generator-separator comprise palladium and said electrodes areimmersed in a fused body of aqueous alkali electrolyte.

8. An analysis system according to claim 7 in which said electrodescomprise an alloy of palladium and silver.

9. An analysis system according to claim 7 in which said cathode is atubular element having a closed end immersed in said electrolyte, and anopen output end extending therefrom, said anode is a tubular elementsurrounding said cathode having an open inlet end and an open outlet endextending from said electrolyte whereby a dispersion of sample inhydrogen carrier gas enters said anode, the hydrogen permeates throughthe wall of the anode tube, across the electrolyte through the wall ofthe cathode and recycles through the cathode output to the inlet of thecolumn, and the sweep gas from the auxiliary generator sweeps the samplefrom the outlet end of the anode into the detector means.

10. A method of analyzing a vaporous sample comill prising the steps of:

circulating hydrogen carrier gas through a continuous circuit includinga gas chromatographic column and an electrolytic hydrogengeneratorseparator including a selectively hydrogen permeable anodeelectrode and a selectively hydrogen permeable cathode electrodecontaining an electrolyte capable of transferring hydrogen between saidelectrodes;

introducing a vaporous sample into the circuit immediately before saidcolumn; electrolytically generating a flow of hydrogen sweep gas inexcess of the amount of hydrogen carrier gas in said circuittransferable through said anode across said electrolyte and through saidcathode;

introducing said sweep gas into the circuit at the inlet to said anode;

removing a dispersion of sample in sweep gas from the circuit;

analyzing said dispersion;

sensing the rate of separation of hydrogen gas through said anode anddeveloping a signal indicative thereof; and

controlling the amount of hydrogen sweep gas introduced in the circuitin response to said signal.

11. A method according to claim 10 in which the sensing step comprisesdeveloping an electrical control signal indicative of the pressure ofthe gas leaving the anode and applying said signal to control the outputof an auxiliary hydrogen generator.

12. A method according to claim 11 in which the output from the columnis delivered to the anode, substantially all of the hydrogen carrier gasis transferred through the anode, across the electrolyte and through thecathode and recycled to the inlet end of the column, and the sweep gasis introduced into the inlet end of the anode and sweeps the sample intoa detector for analyzing the dispersion of samples in said sweep gas.

13. A method according to claim 11 in which the electrodes in thegenerator-separator comprise a hydrogen permeable alloy of palladium andare immersed in an electrolyte capable of transferring hydrogen betweenthe electrodes under the conditions of operation of thegenerator-separator.

14. A method according to claim 12 in which the.

generator-separator separates 99.96 percent of the hydrogen carrier gasin said circuit.

15. A method according to claim 14 in which the sweep gas flow rate isat a rate between 0.01 to 1.0 ml

per minute of hydrogen.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION" Patent Ne.3,858,435 Dated aanuaivmlsfis Invent fl Mario R. Stevens It is certifiedthat error' appears-in theabove-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 8, line 1, after "0.1" insert line2'5,

change "'en'chanced" to --enhanced--. Column 10, line 49-, change "0.01"to --0.l--. V

Signed and sealed this 4th day 'of March 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting OfficerV and Trademarks FORM PO-105O (10- u scoMM-Dc suave-pee "v5. GQVERNMENTPRNf|HG OFFICE .959 0-365-33

1. An analysis system comprising: a closed hydrogen circuit including agas chromatographic column and an electrolytic hydrogen carrier gasgenerator-separator including a selectively hydrogen permeable anodeelectrode and cathode electrode, the inlet to the column being connectedto the hydrogen carrier gas output from said cathode and the outlet fromsaid column being connected to a first inlet end of said anode; sampleinlet means connected to said circuit upstream of said column inlet; anauxiliary electrolytic hydrogen generator having a sweep gas hydrogenoutput connected to the first end of said anode; detector meansconnected to the second end of said anode for receiving and analyzing adispersion of samples in said sweep gas; pressure detector means forsensing the pressure of the second outlet end of said anode anddeveloping an electrical signal indicative thereof; and electricalcontroller means receiving said signal for controlling the output ofsaid auxiliary generator.
 2. An analysis system according to claim 1 inwhich said controller means includes a first output element forproviding a substantially constant control signal for providing aminimum constant flow rate of hydrogen sweep gas in excess of the amountof gas permeating through the anode of the generator-separator.
 3. Ananalysis system according to claim 2 in which said pressure detectormeans includes a transducer for developing an electrical signalinversely proportional to said pressure change and said controllerincludes a second control element for developing a control signal forchanging the flow rate of said auxiliary generator above said minimumrate in response to changes in the hydrogen flow rate change throughsaid anode.
 4. An analysis system according to claim 1 in which saiddetector means is an ionization cross-section detector.
 5. An analysissystem according to claim 1 in which said auxiliary generator is anelectrolytic cell for the electrolytic decomposition of water intohydrogen and oxygen.
 6. A system according to claim 5 in which saidauxiliary hydrogen generator includes a palladium-silver electrodeselectively permeable to hydrogen.
 7. An analysis system according toclaim 1 in which the electrodes of said generator-separator comprisepalladium and said electrodes are immersed in a fused body of aqueousalkali electrolyte.
 8. An analysis system according to claim 7 in whichsaid electrodes comprise an alloy of palladium and silver.
 9. Ananalysis system according to claim 7 in which said cathode is a tubularelement having a closed end immersed in said electrolyte, and an openoutput end extending therefrom, said anode is a tubular elementsurrounding said cathode having an open inlet end and an open outlet endextending from said electrolyte whereby a dispersion of sample inhydrogen carrier gas enters said anode, the hydrogen permeates throughthe wall of the anode tube, across the electrolyte through the wall ofthe cathode and recycles through the cathode output to the inlet of thecolumn, and the sweep gas from the auxiliary generator sweeps the samplefrom the outlet end of the anode into the detector means.
 10. A methodof analyzing a vaporous sample comprising the steps of: circulatinghydrogen carrier gas through a continuous circuit including a gaschromatographic column and an electrolytic hydrogen generator-separatorincluding a selectively hydrogen permeable anode electrode and aselectively hydrogen permeable cathode electrode containing anelectrolyte capable of transferring hydrogen between said electrodes;introDucing a vaporous sample into the circuit immediately before saidcolumn; electrolytically generating a flow of hydrogen sweep gas inexcess of the amount of hydrogen carrier gas in said circuittransferable through said anode across said electrolyte and through saidcathode; introducing said sweep gas into the circuit at the inlet tosaid anode; removing a dispersion of sample in sweep gas from thecircuit; analyzing said dispersion; sensing the rate of separation ofhydrogen gas through said anode and developing a signal indicativethereof; and controlling the amount of hydrogen sweep gas introduced inthe circuit in response to said signal.
 11. A method according to claim10 in which the sensing step comprises developing an electrical controlsignal indicative of the pressure of the gas leaving the anode andapplying said signal to control the output of an auxiliary hydrogengenerator.
 12. A method according to claim 11 in which the output fromthe column is delivered to the anode, substantially all of the hydrogencarrier gas is transferred through the anode, across the electrolyte andthrough the cathode and recycled to the inlet end of the column, and thesweep gas is introduced into the inlet end of the anode and sweeps thesample into a detector for analyzing the dispersion of samples in saidsweep gas.
 13. A method according to claim 11 in which the electrodes inthe generator-separator comprise a hydrogen permeable alloy of palladiumand are immersed in an electrolyte capable of transferring hydrogenbetween the electrodes under the conditions of operation of thegenerator-separator.
 14. A method according to claim 12 in which thegenerator-separator separates 99.96 percent of the hydrogen carrier gasin said circuit.
 15. A method according to claim 14 in which the sweepgas flow rate is at a rate between 0.01 to 1.0 ml per minute ofhydrogen.